From 0eef1c5c4bcd016c48d0d729ca54bae704eef980 Mon Sep 17 00:00:00 2001
From: nzfeng <nfeng@andrew.cmu.edu>
Date: Tue, 1 Jul 2025 13:35:20 -0400
Subject: [PATCH] Fix bug in signed fast marching when curve lies on a boundary
 edge

---
 src/surface/fast_marching_method.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/surface/fast_marching_method.cpp b/src/surface/fast_marching_method.cpp
index 6c8de707..417e782a 100644
--- a/src/surface/fast_marching_method.cpp
+++ b/src/surface/fast_marching_method.cpp
@@ -93,7 +93,7 @@ VertexData<double> FMMDistance(IntrinsicGeometryInterface& geometry,
           // These vertices might themselves lie on the curve, in which case we overwrite them below.
           Halfedge he = commonEdge.halfedge();
           signs[he.next().tipVertex()] = (he.vertex() == pA.vertex) ? -1 : 1;
-          signs[he.twin().next().tipVertex()] = -signs[he.next().tipVertex()];
+          if (!commonEdge.isBoundary()) signs[he.twin().next().tipVertex()] = -signs[he.next().tipVertex()];
         } else {
           Face commonFace = sharedFace(pA, pB);
           if (commonFace == Face()) {